Severe trauma and disease can lead to significant amounts of bone loss. In some instances, it is necessary to excise intercalary bone from a long bone, that is, part of the diaphysis or bone shaft between the ends of the long bone, but it is not necessary to excise the ends of the long bone. Thus, for example, a portion of the shaft of the femur may need to be excised to remove a malignancy, while the ends of the femur defining parts of the hip and knee joint may be healthy. Similarly, it may be necessary to excise part of the shaft of the tibia or humerus while the ends of these bones are healthy. Rather than remove the healthy ends of the bone, it may be desirable to leave the healthy portions of the bone in place and remove the damaged or diseased bone. In these circumstances, the empty span between the ends of the bone must be replaced with some type of mid-shaft prosthesis that spans the distance between the native bone ends. The mid-shaft prosthesis can include stems that fit into the intramedullary canals of the native bone ends and a body that extends between these stems. However, it may be difficult to implant such a mid-shaft prosthesis. Implantation can require that the native bone ends be distracted proximally and distally in order to fit the mid-shaft prosthesis into position. Since the native bone ends are surrounded by and connected to soft tissue, distraction of the native bone ends can damage the soft tissue and the connections between the soft tissue and the native bone ends.
During surgical procedures to replace part of a bone with a prosthesis, orthopaedic trials are typically used. A surgeon uses an orthopaedic trial to ensure that the proper implant size will be used, to make the appropriate cuts and reams in the bone, and to ensure a proper alignment and component thickness prior to implanting the prosthetic components.
For orthopaedic trials to be most useful, it is desirable that they replicate the sizes and shapes of the final implant components to be used. Therefore, it is desirable that orthopaedic trials offer the same flexibility as offered by the final implants. To optimize the utility of such orthopaedic trials, it is also desirable that these orthopaedic trials also be easily and quickly assembled or connected and disassembled or disconnected.
For orthopaedic trials that are sized and shaped to mimic final intercalary implant components, the mid-shaft trials can include stems that fit into the intramedullary canals of the native bone ends and a trial body that extends between these stems. However, as described above with respect to intercalary implants, it may be difficult to insert such a mid-shaft trial without damaging the soft tissue at the native bone ends.